Chain saws, brush cutters and trimmers, among others, are known as work apparatuses with a compact internal combustion engine. U.S. Pat. No. 5,595,153 (Patent Document 1) relates to a hood for covering an open top end of a body case that incases and encircles an internal combustion engine and an adjacent air filter box. This patent proposes a hood having a front end pivoted about a pivot axis held on the body case and having an open/close knob at its rear end. The open top end of the body case can be uncovered by unlocking the engagement of the hood with the body case at the open/close knob and then rotating the hood upward about the pivot axis at the front end. The pivot axis at the front end of the body case can be locked at or released from a bearing portion of the body case. The bearing portion of the body case has a channel-shaped configuration opening rearward in its side view. When the hood is moved rearward, the pivot axis disengages from the channel-shaped bearing portion through its back-faced aperture, and the hood can be removed from the body case.
Japanese Patent Laid-open Publication No. 2006-125405 (Patent Document 2 equivalent to U.S. Pat. No. 7,424,879) discloses an invention that is common to the Document 1 in that the front end of the hood is pivotally supported on the body case. A difference between these Patent Documents lies in that Patent Document 2 uses a slider linearly movable back and forth instead of the open/close knob of Patent Document 1 to lock and release the hood relative to the case body by operating the slider.
Patent Documents 1 and 2 have an advantage permitting a user to access to the air filter box or an engine by opening the hood without a tool. However, such a structure for pivotally supporting one end of a hood to a case body as employed by Patent Documents 1 and 2 involves the problem that the bearing portion of the case body is liable to break.
Especially in Patent Document 1, the side-viewed channel-shaped bearing has a larger possibility to break because of a load applied upon receiving or releasing the pivot axis. To prevent it, the bearing portion needs a design having a high strength.